In the prior art, solenoids are generally used as the driver to lock or unlock electromechanical door latches or strikes. The solenoid is spring biased to either a default locked or unlocked state, depending on the intended application of the lock. When power is applied to the solenoid, the solenoid is powered away from the default state to bias a return spring. The solenoid will maintain the bias as long as power is supplied to the solenoid. Once power has been intentionally removed, or otherwise, such as through a power outage from the grid or as a result of a fire, the solenoid returns to its default locked or unlocked state.
In a fail-safe lock system, power is supplied to the solenoid to lock the door latch mechanism. With power removed, a return spring moves the latching mechanism to an unlocked state. Thus, as long as the latch remains locked, power has to be supplied to the solenoid to maintain stored energy in the return spring. Typically, this power requirement equates to about 0.5 A to hold the solenoid plunger in the latch-locked state. This hold power is in addition to the approximately 1.0 A needed to initially pull in the plunger upon energizing of the solenoid.
In a fail-secure system, the reverse is true. With power removed, the return spring moves the latching mechanism to a locked state. Thus, as long as the latch remains unlocked, power has to be supplied to the solenoid to maintain stored energy in the return spring. Again, about 0.5 A is required to hold the solenoid plunger in the latch-locked state (with about a required 1 A to initially pull in the plunger).
A system designed to overcome the shortcomings of solenoid lock systems is disclosed in the prior art disclosure of Sargent Manufacturing Company (WO2014/028332—herein referred to as “the '332 publication”), the entirety of which is incorporated herein by reference. As disclosed in the '332 publication, the solenoid used to drive the door latch mechanism is swapped out for a small DC motor that moves a latching plate. This change, in combination with the motor aligning with and engaging an auger/spring arrangement, reduced standby power consumption of the driver from about 0.5 A to about 15 mA.
Nonetheless, there still exists a need for a compact power control circuit assembly, offering further improved power efficiency for use with electric door lock systems. The present invention fills these and other needs.